eight / solution 8.1

<?php

function verifyEmail(string $e)
{
    // check for basic pattern ([email protected])
    if (!preg_match("/.+@.+\..+/", $e)) {
        return false;
    }

    // convert to lowercase
    $e = mb_convert_case($e, MB_CASE_LOWER);

    // eliminate whitespace
    $e = preg_replace("/\s+/", "", $e);

    // simplify consecutive periods
    $e = preg_replace("/\.+/", ".", $e);

    // split email into name and domain because their constraints are different
    $name = explode("@", $e)[0];
    $domain = explode("@", $e)[1];

    // check for both elements
    if (!strlen($name) || !strlen($domain)) {
        return false;
    }

    // remove leading/trailing periods
    $name = trim($name, ".");
    $domain = trim($domain, ".");

    // remove invalid characters from both sections
    $name = preg_replace("/[^a-z0-9!#%\$&\'\*\+\-\/\=\?\^_`\{|\}~\.]/", "", $name);
    $domain = preg_replace("/[^a-z0-9\-\.]/", "", $domain);

    // crop name to 64 characters
    $name = substr($name, 0, 64);

    // crop each domain segment to 63 characters
    $domain = explode(".", $domain);
    foreach ($domain as &$i) {
        $i = substr($i, 0, 63);
    }
    $domain = implode(".", $domain);

    // check for both elements again (in case all characters were invalid)
    if (!strlen($name) || !strlen($domain)) {
        return false;
    }

    // rebuild email
    $e = $name . "@" . $domain;

    return $e;
}

print_r(verifyEmail("  a GJF [email protected]. ") . "\n");